In less than a day this week, Hurricane Idalia strengthened from a Category 1 storm into a fierce Category 4, the second-highest tier for cyclones.
It ultimately made landfall in the United States as a powerful Category 3 storm — the threshold for a “major hurricane” — with wind speeds whipping at approximately 193 kilometres per hour (120 miles per hour).
With the Atlantic hurricane season only now entering its peak months, experts are questioning whether Idalia is a sign of what’s to come, as climate change supercharges severe weather events.
Idalia, the third hurricane and ninth named storm of the season, has since drifted off into the North Atlantic Ocean, having weakened into a post-tropical cyclone.
As of Friday morning, it was 295 kilometres (185 miles) west of the British territory of Bermuda, with maximum sustained winds of about 95km/h (60mph). The island is expected to receive between 75 and 125 millimetres (3 to 5 inches) of rainfall through Sunday, with the potential for flash flooding.
But the destruction Idalia wrought as it passed through the southern US has scientists readjusting their expectations for the 2023 hurricane season.
What they initially believed would be a relatively mild hurricane season is now projected to have more extreme storm activity.
Hurricane Idalia swept through the southern United States in the early hours of Wednesday, unleashing fierce winds, heavy rainfall and widespread flooding in the states of Florida and Georgia. Even after being downgraded into a tropical storm, it walloped South and North Carolinas, inundating major coastal cities like Charleston.
In May, the US National Oceanic and Atmospheric Association (NOAA) predicted a “near-normal” Atlantic hurricane season. But in August, just weeks before Idalia formed, NOAA bumped up its forecast, increasing the number of storms anticipated for the season.
Between 14 and 21 named storms — with winds of 63km/h (39mph) or more — are now expected for 2023. Of those, the agency said that six to 11 could become hurricanes, and two to five could become major hurricanes, defined as Category 3 or above.
As cleanup continues in the areas ravaged by Idalia, how has climate change played a role in the development of powerful storms? And what could this mean going forward? Let’s take a look.
Why are scientists now expecting a more severe storm season?
After seven straight years of predicting record hurricane seasons, scientists initially thought 2023 would mark an ease-up.
This year brought the arrival of El Niño, a climate pattern that typically has a moderating effect on hurricane season in the southern US. Hurricanes require consistent wind patterns to form — and El Niño, with its stronger westerly winds, can end up shearing off the tops of Atlantic storms before they fully form into cyclones.
In some parts of Florida, surface water temperatures rose to more than 38 degrees Celsius (101 degrees Fahrenheit) — leading observers to compare its beaches to hot tubs.
Those extreme temperatures have effectively cancelled out some of the moderating effects of El Niño, causing scientists to revise their expectations and warn of a more severe storm season.
What role does climate change play in hurricanes?
Every storm is different, and scientists have yet to determine whether climate change was a significant factor in the intensity or behaviour of Idalia.
But scientists do say that climate change has contributed to conditions that have fuelled higher wind speeds and rainfall levels during hurricanes. Politicians have underscored the connection as well.
“I don’t think anybody can deny the impact of the climate crisis any more,” US President Joe Biden said in a news conference earlier this week. “Just look around: historic floods, more intense droughts, extreme heat, significant wildfires that cause significant damage like we’ve never seen before.”
Warming ocean surface temperatures, for example, can add to the intensity of a hurricane and help drive stronger winds.
Scientists with NOAA believe that if the planet warms by 2 degrees Celsius above the preindustrial average, hurricane wind speeds could increase by 10 percent.
Climate change may also be slowing down the pace at which hurricanes move, meaning that storms can dump more water on the places they pass through.
A warmer atmosphere retains greater levels of moisture, meaning that water builds up in clouds until finally breaking and dumping large portions of rain.
A 2022 study in the journal Nature Communications found that, during the especially active 2020 Atlantic hurricane season, climate change increased hourly rainfall rates by between eight and 11 percent.
What challenges do communities face in the aftermath of hurricanes?
Hurricanes such as Idalia often leave extensive damage in their wake, with cleanup and recovery efforts taking weeks and even months to complete.
In a news conference on Wednesday, Deanne Criswell, administrator of the Federal Emergency Management Agency (FEMA), said Idalia made landfall with winds of up to 193km/h (120mph) and as much as 25.4 centimetres (10 inches) of rain. Emergency rescue teams worked to reach dozens of people trapped in their homes by floodwaters.
“Idalia is the strongest storm to hit this part of Florida — to make landfall in this part of Florida in over 100 years,” said Criswell.
— FEMA (@fema) September 1, 2023
Insurance claims from storm-related damage are expected to surpass $10bn, and the storm could heighten concerns over whether insurance companies may start to see states like Florida as too risky to justify offering their services.
More immediately, communities are working to clear mud and debris and restore infrastructure services such as electrical power. According to the website PowerOutage.us, more than 84,000 households remain without power in Florida.
But some parts of Florida that faced impacts from Idalia were still recovering from the previous year’s hurricanes. Southwest Florida was pummelled in September 2022 when Hurricane Ian landed as a Category 4 storm, killing more than 150 people and causing $112bn in damage — a record for the state.
“We’re about 11 months out of Hurricane Ian,” Mayor Kevin Anderson of Fort Myers, Florida, told ABC News this week. “And we’ve still got a lot of blue tarps and a lot of sites that are under construction.”
He estimated that recovery would take anywhere from five to 10 years. “It’s a very long process,” he said.